Composite lightning strike protection system

ABSTRACT

A porous metal and carbon composite lightning strike protection system is described that utilizes flexible metallic material and porous carbon. The carbon-based lightning strike protection system may be produced in the form of a panel that may be applied over the surface of an object to be protected or may be created directly over the surface of the object. The carbon-based lightning strike protection system is readily adaptable to high temperature applications.

FIELD OF THE INVENTION

The present invention is directed to a composite lightning strikeprotection system that may be applied to the surface of an object suchthat the composite lightning strike protection system reduces damage tothe object when subjected to a lightning strike.

SUMMARY OF THE INVENTION

The present invention includes a lightning strike protection systemcomprising a metallic spreader shield layer comprising a flexiblemetallic material, and a porous carbon thermal insulating layercomprising carbon foam having a thermal conductivity below about 0.5W/mK, wherein the porous carbon thermal insulating layer is positionedbetween the metallic spreader shield layer and a surface of an object tobe protected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of the composite lightningstrike protection system in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Some preferred embodiments of the present invention are described inthis section in detail sufficient for one skilled in the art to practicethe present invention without undue experimentation. It is to beunderstood, however, that the fact that a limited number of preferredembodiments are described in this section does not in any way limit thescope of the present invention as set forth in the claims.

It is to be understood that whenever a range of values is describedherein, i.e. whether in this section or any other part of this patentdocument, that the range includes the end points and every pointtherebetween as if each and every such point had been expresslydescribed. Unless otherwise stated, the words “about” and“substantially” as used herein are to be construed as meaning the normalmeasuring and/or fabrication limitations related to the value orcondition which the word “about” or “substantially” modifies. Unlessexpressly stated otherwise, the term “embodiment” is used herein to meanan embodiment of the present invention.

The present invention is directed to a composite system that canmitigate lightning strike damage to an object. With reference to FIG. 1there is illustrated a composite lightning strike protection system 10in accordance with an embodiment of the invention. In general, thecomposite lightning strike protection system includes a metallicspreader shield layer 12 and a porous carbon thermal insulating layer 14positioned between the metallic spreader shield layer 12 and the surface16 of an object 17 to be protected.

The metallic spreader shield layer 12 is a layer made of flexiblemetallic material. In preferred embodiments, the flexible metallicmaterial may include, but is not limited to copper, aluminum or alloysthereof. The flexible metallic material may be in the form of anexpanded metal sheet, a perforated metal sheet, a welded wire mesh, or awoven wire mesh. The thickness of the metallic spreader shield layer 12is preferably less than 1 mm, and may range from about 0.2 mm to about 1mm. In some embodiments, a suitable flexible metallic includes, but isnot limited to, copper or aluminum expanded metal foils.

A porous carbon thermal insulating layer 14 is positioned between themetallic spreader shield layer 12 and the surface 16 of an object to beprotected. The porous carbon thermal insulating layer provides thermalinsulating properties to protect the object from excessive heat. Theporous carbon thermal insulating layer comprises a porous carbonmaterial such as a carbon foam. Preferably, the porous carbon materialexhibits a porosity of at least 80%, and in some embodiments of at least90%. In preferred embodiments, the porous carbon thermal insulatinglayer exhibits a thermal conductivity below about 0.5 W/mK. Thethickness of the porous carbon thermal insulating layer is notparticularly limited and may be based on the particular application. Incertain embodiments the thickness of the porous carbon thermalinsulating layer ranges from about 0.2 to about 0.5 inches.

An adhesive layer 18 is used to adhere the metallic spreader shieldlayer 12 to the porous carbon thermal insulating layer 14. The adhesiveused for the adhesive layer 18 depending on the expected temperaturesthe adhesive is expected to experience for the particular application.For high-temperature applications involving temperatures above the glasstransition temperature of epoxy adhesive or other polymer resins, agraphite adhesive is preferable In some embodiments, a suitable graphiteadhesive exhibits a use temperature of at least about 350 C, in furtherembodiments exhibits a use temperature of at least 1000 C, and stillfurther exhibits a use temperature of at least about 2000 C. The usetemperature is the temperature or range of temperatures at which thegraphite adhesive substantially maintains its physical and chemicalproperties and continues to provide its function as an adhesive. Forlower temperature applications, where the temperatures are less than 350C, polymeric epoxies may be utilized.

It may be desirable to provide a cover layer 20 over the metallicspreader shield layer 12 to protect the metallic spreader shield layerfrom damage. In certain embodiments the cover layer may be a coating ofa polymeric material or a layer of polymeric film. In preferredembodiments, the cover layer 20 may include but is not limited to, acarbon fiber reinforced prepreg or a glass fiber reinforced prepreg.

In the embodiment illustrated in FIG. 1, the composite lightning strikeprotection system 10 is in the form of a panel that may be applied tothe surface of the object to be protected. The panel may be preparedahead of time in the desired shape and form required and subsequentlyadhered to the surface of the object. In this way, objects may be easilyretrofitted with the composite lightning strike protection system of thepresent invention. Alternatively, the composite lightning strikeprotection system may be applied and assembled directly on the surfaceof the object to be protected.

While several embodiments of the present invention have been shown anddescribed, it will be obvious to those skilled in the art that manychanges and modifications may be made thereunto without departing fromthe spirit and scope of the invention as described in the claims. AllUnited States patents and patent applications, all foreign patents andpatent applications, and all other documents identified herein areincorporated herein by reference as if set forth in full herein to thefull extent permitted under the law.

What is claimed is:
 1. A lightning strike protection system, comprising:a metallic spreader shield layer, wherein the metallic spreader shieldlayer comprises flexible metallic material; and a porous carbon thermalinsulting layer comprising carbon foam having a thermal conductivitybelow about 0.5 W/mK and a thickness not greater than about 0.5 inches,wherein the porous carbon thermal insulating layer is positioned betweenthe metallic spreader shield layer and a surface of an object to beprotected.
 2. The lightning strike protection system of claim 1, whereinthe flexible metallic material is selected from the group consisting ofcopper and aluminum.
 3. The lightning strike protection system of claim1, wherein the flexible metallic material is in the form selected fromthe group consisting of expanded metal, perforated metal, welded wiremesh, and woven wire mesh.
 4. The lightning strike protection system ofclaim 1, wherein the thickness of the metallic spreader shield layer isless than about 1 mm.
 5. The lightning strike protection system of claim1, further comprising an adhesive between the metallic spreader shieldlayer and the porous carbon insulating layer.
 6. The lightning strikeprotection system of claim 5, wherein the adhesive is a graphiteadhesive exhibits a use temperature of at least about 1000 C.
 7. Thelightning strike protection system of claim 5, wherein the adhesive isan epoxy adhesive.
 8. The lightning strike protection system of claim 1,wherein the thickness of the flexible metallic material has a valueranging from about 0.25 mm to about 1 mm.
 9. The lightning strikeprotection system of claim 1, further comprising a cover layer, whereinthe metallic spreader shield layer is positioned between the cover andthe porous carbon thermal insulating layer.
 10. The lightning strikeprotection system of claim 2, wherein the cover layer is selected fromthe group consisting of carbon fiber prepregs and glass fiber prepregs.